CN111512093B

CN111512093B - Control system for HVAC including air handling unit and terminal unit and method of operating the control system

Info

Publication number: CN111512093B
Application number: CN201880083398.6A
Authority: CN
Inventors: 詹姆斯·J·库根
Original assignee: Siemens Industry Inc
Current assignee: Siemens Industry Inc
Priority date: 2017-12-28
Filing date: 2018-11-12
Publication date: 2023-12-01
Anticipated expiration: 2038-11-12
Also published as: US10458672B2; CA3087134C; US20190203964A1; CN111512093A; CA3087134A1; EP3707438A1; EP3707438B1; WO2019133118A1

Abstract

Instead of complex modeling or time consuming repeated measurements for optimizing HVAC systems, the slope or change in energy usage according to a change in a variable (e.g., temperature or humidity) is used to adjust the variable. In an HVAC system, the temperature or humidity of supplied air from an AHU (12) is set based on the derived slope. The energy usage of heating and/or cooling air to be supplied by the AHU (12) is utilized to balance the energy usage of heating and/or cooling the supplied air at the terminal unit (22). The slope of the total energy usage may be indicated by the sum of the flow rates.

Description

Control system for HVAC including air handling unit and terminal unit and method of operating the control system

Technical Field

Embodiments of the present invention relate generally to heating, ventilation and air conditioning (HVAC) systems.

Background

To distribute air in an HVAC system, an air distribution system moves and conditions the air. An Air Handling Unit (AHU) includes heating coils, cooling coils, and fans for mixing outside air, heating or cooling air, and moving the air to an area, room, or other area local to a user space. The terminal units in the area, room or other area local to the user space also include heating coils, cooling coils and fans for further heating or cooling the air and outputting the air to the user space.

HVAC systems consume considerable energy. The amount of energy used depends on the operating state of the system, including the operating states of the AHU and the end unit. An optimization technique explicitly calculates the value of the cost function at the candidate operating point and selects the operating point that causes the system to repeatedly move to a lower cost. Another optimization technique uses a set of heuristic rules instead of a complete model. In another optimization technique, a mathematical description of the cost function is analyzed to calculate the operating points that minimize the function. As yet another optimization technique, the energy consumption of the various physical components is physically measured at different operating points, and then the optimization logic calculates the next operating point by comparing the energy consumption at the most recent operating point. Identifying and using operating states that minimize energy usage while meeting other objectives, while valuable, is difficult and often overly complex.

Disclosure of Invention

Instead of complex modeling or time consuming repeated measurements, the slope or change of energy usage according to changes in the variable (e.g., temperature or humidity) is used to adjust the variable. In HVAC systems, the temperature or humidity of the supplied air from the AHU is set based on the slope. The energy usage of heating and/or cooling air to be supplied by the AHU is utilized to balance the energy usage of heating and/or cooling the supplied air at the terminal unit. The slope of the total energy usage may be indicated by the flow rate.

In a first aspect, a control system for heating, ventilation, and air conditioning (HVAC) is provided. An Air Handling Unit (AHU) has an AHU heating coil and an AHU cooling coil. The AHU is configured to supply air at an AHU temperature output. The terminal unit has a terminal flow rate sensor, a terminal heating coil, and a terminal cooling coil. The terminal unit is connected to the air handling unit by a conduit for receiving air from the AHU. The controller is configured to receive the flow rate from the terminal flow rate sensor, calculate a slope of the power consumption based on the flow rate, and set the AHU temperature based on the slope.

In a second aspect, a method for optimizing heating, ventilation, and air conditioning (HVAC) is provided. An air amount for heating or cooling air supplied to each terminal by the air treatment unit is received. The slope of the energy usage of the terminal and the air handling unit is calculated from the amount of air. The air supply temperature or humidity of the air handling unit is adjusted based on the slope.

In a third aspect, a control system for heating, ventilation, and air conditioning (HVAC) is provided. An Air Handling Unit (AHU) has an AHU flow rate sensor, an AHU heating coil, and an AHU cooling coil, the AHU configured to supply air to a terminal at an AHU temperature. The controller is configured to receive flow rates from the AHU flow sensor and the terminal flow sensor, calculate a slope of power consumption based on the flow rates, and set the AHU temperature based on the slope.

Other systems, methods, and/or features of the present embodiments will be or become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. Additional features of the disclosed embodiments are described in, and will be apparent from, the following detailed description and the accompanying drawings.

Drawings

The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the embodiments. In the drawings, like reference numerals designate corresponding parts throughout the different views.

FIG. 1 is a block diagram of one embodiment of a control system for air handling in an HVAC system;

FIG. 2 is a graph showing the slope of temperature differences and energy consumption that may be derived and used by the control system of FIG. 1; and

FIG. 3 is one embodiment of a method for HVAC optimization.

Detailed Description

The energy usage of the AHU system is optimized. Instead of computing the optimal operating point, a hill climbing technique is used, and iterations are used to repeatedly determine and move in a direction toward a lower cost point. Unlike some hill climbing techniques, this does not require a complete calculation of the cost function. Instead, the current slope of the cost versus controlled variable is used. The slope is the sum of the slopes calculated for each energy consuming component.

In one embodiment, data from the air terminals is collected to determine the slope of energy usage versus supply air temperature. These slopes are easily collected by knowing how much air is used by each air terminal and whether the air terminal is heating or cooling the air. Knowing the total amount of air re-heated at the terminal provides the dynamic data needed to optimize the system. The conditions at the terminals determine the slope of the total energy usage. By adjusting the supply air temperature from the AHU based on the slope, a zero or near zero slope region is found that represents the optimal energy usage tradeoff between AHU and end operation.

The calculation is simple. The sum of the air flows provides a slope of energy usage rather than solving a cost function or performing mathematical optimization to minimize the cost function. Data for calculation is easily collected from the terminal.

FIG. 1 illustrates one embodiment of a control system 10 for an HVAC. The system 10 optimizes energy consumption as a balance between the AHU 12 and the terminal unit 22. The slope of the energy consumption variation as a function of the temperature of the system as a whole is used to adjust or maintain the temperature of the air supplied by the AHU 12.

The control system 10 implements the method of fig. 3. Other methods may be implemented in the control system.

Control system 10 includes an AHU 12, a plurality of terminal units 22, and a conduit network 20 interconnecting AHU 12 and terminal units 22 for air flow from AHU 12 to terminal units 22. Additional, different, or fewer components may be provided. For example, any number of terminal units 22 are provided, such as three or more (e.g., several tens). As another example, a separate or remote computer or server is provided to integrate with the AHU 12 (such as with the controller 14 of the AHU 12) and/or the terminal unit 22 and calculate settings and/or slope for optimizing energy usage of the AHU 12. In yet another example, a wired and/or wireless communication network is provided for transmitting data from the AHU 12 and/or the end units 22 and/or transmitting data between the AHU 12 and/or the end units 22.

AHU 12 may be any now known or later developed AHU for residential, industrial, or office use. The AHU 12 mixes air from outside the building or supply air from a heating/cooling source with return air from the space in which the terminal unit 22 is located, conditions the air, and then provides the conditioned air to the terminal unit 22.AHU 12 may be a dedicated outside air system that conditions only outside air for supply to the terminal units.

The AHU 12 includes a return air input, a fresh air input (i.e., receiving air from the outside), an air mixing section, a filter, one or more cooling coils 17, one or more heating coils 16, dampers 13 or actuators, attenuators, exhaust, one or more fans 18, and one or more sensors 19. Additional, different, or fewer components may be provided in the AHU 12, such as no more than one heating or cooling coil and/or heat recovery device. For example, the AHU 12 is a tank with dampers, fans 18, and one or both of heating coil 16 and cooling coil 17, with or without filters, mixing sections, and/or attenuators. In another example, sensor 19 is not provided as a flow sensor, and therefore the AHU flow rate is determined based on the terminal flow rate or other source.

The heating coil 16 and the cooling coil 17 are connected by piping for the chilled and heated water supply and return. Heating and/or cooling without water may be provided, such as heating coils 16 and cooling coils 17 based on chilled and heated air. In another embodiment, the heating coil 16 is heated using electricity or gas (e.g., a burner). The cooling coil 17 may be cooled using a condenser.

The fan 18 for air distribution is any fan that forces air into the duct 20. The fan 18 includes blades and a motor. Any blade may be used. Any motor may be used. In one embodiment, the motor is a variable drive, such as a Variable Frequency Drive (VFD), operatively connected to the controller 14. The motor controls the speed of the fan 18 in response to a control signal, such as in response to a frequency, duty cycle, amplitude, or other signal characteristic. The actuator controls the damper 13 to increase and/or decrease the air flow. Alternatively or additionally, a change in the speed of the fan 18 causes a greater or lesser air flow. The rate of air flow controls the temperature of the air passing from the AHU 12 due to heat transfer. The change in air flow of the fan 18 may be used to more closely regulate the temperature downstream of the fan 18 in the air distribution.

The AHU 12 includes one or more controllers 14. The controller 14 is a field panel, processor, computer, application specific integrated circuit, field programmable gate array, analog circuit, digital circuit, or other controller. A single controller 14 is shown, but an arrangement of different controllers may be used. For example, different controls are provided for the different components (e.g., the controls for the fan 18 are different than the controls for the damper, heating coil 16, or cooling coil 17). The distributed controllers may communicate for interactive control, may be controlled by a master controller, and/or may operate independently of other controls.

Memory 11, such as Random Access Memory (RAM), read Only Memory (ROM), removable media, flash memory, solid state memory, or other memory, stores instructions for use by controller 14. For example, the memory 11 is a non-transitory computer-readable storage medium for storing instructions. When the physical controller 14 executes instructions, the controls discussed herein are performed. For example, memory 11 includes instructions for implementing an AHU control manager 21 that calculates a slope and sets an air supply temperature. The memory stores set points, sensor values, control information, and/or instructions for control by the controller 14. Set points, data obtained from sensors 19, 29, or other operational metrics of AHU 12 may be stored. The stored data is used to control the operation of the AHU 12, such as to calculate a slope and use the slope to set the temperature of air supplied by the AHU 12 to the terminal unit 22.

The sensor 19 is used to measure the energy consumption. In one embodiment, the sensor 19 is a flow rate sensor. A sensor 19 is positioned in the air duct to measure the flow rate of air through the AHU 12, out of the AHU 12, and/or over the heating coil 16 and/or cooling coil 17. In another embodiment, the sensor 19 is a fan speed sensor such as an optical sensor or encoder to measure the rotation of the fan. In yet another embodiment, the sensor 19 is a strain gauge, contactor, or other sensor to measure the position of the damper. Alternatively, the sensor 19 uses a setting of damper position and/or fan speed (e.g., duty cycle or frequency). The energy consumption is measured in terms of flow rate or air quantity. Any sensor that indicates the flow rate may be used, such as increasing the air flow rate through the terminal.

Terminal unit 22 receives conditioned air supplied by AHU 12 via conduit 20. The terminal unit 22 may further heat or cool the air. For example, the AHU 12 supplies air at 61 degrees. The set point of the air to the user space is 65 degrees so the terminal unit 22 heats the supplied air to 65 degrees and then supplies the air to one or more user zones. The terminal unit 22 includes one or more air outputs to one or more rooms.

The terminal unit 22 includes a damper 23, a controller 24, a heating coil 26, a cooling coil 27, a fan 28, and/or a sensor 29. Each terminal unit 22 is identical to the other terminal units 22, but is arranged to condition air for different zones or rooms. Alternatively, different terminal units 22 have different capacities, components and/or capabilities. Similarly, the terminal unit 22 may be the same as or different from the AHU 12, such as having the same components. The terminal unit 22 may use the same or different types of components labeled for the AHU 12.

Each of the terminal units 22 includes a flow rate sensor 29. A flow sensor 29 is provided that is the same as or different from the flow sensor for AHU 12. The terminal unit 22 also includes heating coils 26 and/or cooling coils 27 for heating or cooling air based on the set point of the user zone.

The controller 14 of the AHU 12 optimizes the energy consumption of the HVAC system. Other controllers may be used, such as a separate server or computer (e.g., HVAC workstation or panel) or the controller 24 of the terminal unit 22. The controller 14 is configured by software (e.g., instructions), hardware, and/or firmware to set the temperature or humidity of the supply air provided to the terminal unit 22 to optimize energy consumption.

Controller 14 is configured to collect data from or for AHU 12 and/or terminal unit 22, such as from sensors 19 and 29. The collected data may also be used for operation of the AHU 12 and/or may be collected for other uses. Controller 14 receives flow rates from AHU sensor 19 and terminal unit sensor 29.

Push, pull or lookup systems may be used. In one embodiment, the sensor readings are provided or stored on a regular basis in a table and updated if changed. The controller 14 accesses the sensor readings from local memory. Alternatively, the terminal unit 12 is queried when a sensor reading is required.

In one embodiment, the terminal units 22 and the AHU 12 are grouped in the communication system using a group data exchange. Communications rely on group tags, such as sensor readings that are routed to or accessed by a group host. For example, AHU 12 is a group host in which terminal unit 22 is a group member. No other group of communications will be read or used, but communications providing the sensor readings for that group will be identified. Any header or group label may be used. Other communication systems may be used, such as a direct connection, a bus, or responding to a query.

The controller 14 is configured to calculate a slope of power consumption according to a controlled variable (e.g., supply air temperature) based on a flow rate (referred to herein as a "slope"). Any controlled characteristics of AHU 12 may be used. For example, the temperature of the supplied air output by the AHU 12 is controlled to optimize the system. Depending on the outside air temperature and the set point of the terminal unit, the total power consumption can be minimized. In another example, the humidity of the supplied air is controlled. In the following example, air temperature is used.

The optimization is performed in a continuous manner. Periodic checks may be performed, such as periodic calculation of the slope. In one embodiment, the optimization is based on a trigger. For example, changes in the outside air temperature and/or temperature set point of one or more of the terminal units 22 trigger optimization.

The optimization is hill climbing optimization. The AHU 12 sets the air temperature of the supplied air based on the slope. After a period of time, the flow rate is again measured and the slope is again calculated. The air temperature is again set based on the resulting slope. This process continues until the slope is determined to be zero or within a threshold tolerance of zero. Alternatively, a slope is calculated and the temperature is set based on the slope without further iteration until another trigger or periodic check is performed.

The optimization determines conditions that minimize the use of heating and cooling in the HVAC system associated with the AHU 12 and the terminal unit 22 of the AHU 12. The temperature of the air supplied by the AHU 12 to the terminal unit 22 is optimized by finding a temperature that minimizes the energy used for heating and cooling.

Power consumption it is assumed that the air flow drawn in by the terminal unit 22 is not affected by the supply air temperature, since the terminal unit 22 does not condition the air flow for temperature control. The power consumed by heating or cooling coils 16, 26, 17, 27 depends on the rate at which the coils transfer heat or cold to or from the air stream. It is assumed that power is proportional to heat transfer rate. The heat transfer rate is proportional to the air flow rate times the change in air temperature effected by the coil. The heat transfer rate is: q=ρcqΔt, where ρ is density, c is specific heat, Q is air flow rate, and Δt is temperature change.

The heat transfer rate is used to determine the slope of the power consumption as a function of temperature. The AHU 12 and the terminal unit 22 each contribute to the overall power consumption. Fig. 2 shows an example of a terminal unit 22 having one AHU 12 and two connections. The x-axis is temperature. The y-axis on the left is the temperature difference across the coils (heating and cooling coils) and the y-axis on the right is the total power. For an AHU 12, a solid line 32 with a downward slope represents cooling and a solid line 34 with an upward slope represents heating. The line is drawn based on a temperature difference from the outside air temperature. During cooling, the heating ramp rate was 0. During heating, the cooling slope was 0. In the example of fig. 2, the outside air temperature is 70 degrees, so the cooling line 32 and the heating line 34 form a "V" shape turning at 70 degrees. Similarly, the terminal unit 22 has a heater wire 36 and a cooling wire 38 that are plotted based on the difference in temperature in the set point and the supply air temperature. In the example of fig. 2, one terminal unit 22 supplies 52 degrees of air to one user space, and the other terminal unit 22 supplies 65 degrees of air to the other user space. The total power consumption line 30 is the sum of power consumption from the components, and thus includes inflection points 40 of 52 degrees, 65 degrees, and 70 degrees. The total power consumption line 30 is plotted based on the power scale of the y-axis on the right side.

Table 1 provides example values for fig. 2. Based on data accessed by the AHU controller for calculating the slope as described herein, table 1 may be generated by the AHU controller and stored in local memory. As shown in Table 1, OAT is the outside air temperature, dT is the temperature difference, h is heating, c is cooling, power is measured air flow rate, tdisc 1 and 2 are temperature set points, and Tdisc AHU is the supply air temperature.

TABLE 1

By determining the slope, the temperature of the supplied air from the AHU 12 to the terminal unit 22 may be optimized. The optimized temperature is any temperature that results in a slope of 0 for the total power consumption. In the example of fig. 2, the optimized temperature of the supply air is between 65 and 70 degrees (see the total power consumption line 40, where the slope is 0).

The slope of the total power consumption according to the air supply temperature is calculated as the sum of the flow rates. The sum of the slopes from each component is the slope of the system 10. At any given temperature, the slope of the system is the sum of heating and cooling. The slope is calculated from the heating sum of the flow rates for heating and the cooling sum of the flow rates for cooling. If heating and cooling are performed with the same efficiency, the sum of all flow rates can be used regardless of heating or cooling.

To calculate the slope of the power consumption 30, the operating efficiency of the heating coils 16, 26 and the cooling coils 17, 27 may be considered. In one embodiment, the heating efficiency is the same for all heating coils 16, 26 and the cooling efficiency is the same for all cooling coils 17, 27. The heating sum is a function of the heating efficiency factor and the cooling sum is a function of the cooling efficiency factor. In other embodiments, the efficiency factor, heating, and/or cooling may be different for different coils and/or between the AHU 12 and the end unit 22. The efficiency factor e may be different for heating systems and cooling systems. The efficiency factor e may also be different for coils in the AHU 12 than for coils in the terminal unit 22. The value of the efficiency factor may be calculated from the energy process employed in the system. Default or design-based efficiency factors may be used. Calibration may be used to set the efficiency factor. In alternative embodiments, the efficiency factor is not included in the calculation of the slope.

Adding the efficiency factor e of the power consumption p to the heat transfer rate yields: p=eq=eρcqΔt=eρcq (T _out –T _in ). The heating h and cooling c are separate. For heating coil 26 in terminal unit 22, numbered i, serviced by AHU 12 (e.g., number i may be 1 or 2 corresponding to first or second terminal unit 22 in fig. 2), the power consumption becomes: if the terminal is heating, p _hi ＝eρcQ _i (T _iout –T _A ) And if the terminal is unheated, p _hi =0. Similarly, for cooling coil 27 in terminal unit 22, numbered i, serviced by AHU 12, the power consumption becomes: if the terminal is cooling, p _ci ＝eρcQ _i (T _iout –T _A ) And if the terminal is not cooled, p _ci ＝0。

Since the heat transfer function is assumed to represent power consumption, the slope of the consumed power versus supply air temperature change is: if the termination unit 22 is heating, dpi/dTA= -e ρcQ _i And if the terminal unit 22 is not heated, dp _i /dT _A =0. If the terminal is heating, define Q _hi ＝Q _i The method comprises the steps of carrying out a first treatment on the surface of the And if the terminal is not heated, 0, obtaining dp _i /dT _A ＝-eρcQ _hi . Similarly, for cooling, dp _i /dT _A ＝-eρcQ _ci 。

Slope of power consumption according to temperature (dp _i /dT _A ) Proportional to the flow rate Q. If eρc is constant, the change in slope with respect to the supply temperature of the power consumed by the heating coil 26 in the terminal unit 22, numbered i, is proportional to the flow of heating air: dp (dp) _i /dT _A And Q is equal to _hi Proportional to the ratio. Similarly, the slope of power consumption in the AHU 12 as a function of temperature for cooling is proportional to air flow.

The total power consumed by all heating coils is the sum of the values of the individual heating coils 16, 26: p is p _hsum ＝ΣeρcQ _hi (T _iout -T _A ). The slope of the total power consumed by the heating coils in all terminals with respect to the change in supply air temperature is: dp (dp) _hsum /dT _A ＝Σ–eρcQ _hi ＝-eρcΣQ _hi . The slope of the total power consumed by the heating coils 16, 26 is proportional to the sum of the values of the heated air flow rate, denoted dp _hsum /dT _A And sigma Q _hi Proportional to the ratio. The same analysis applies to the cooling coils in the terminal unit 22 and the AHU 12, yielding: dp (dp) _csum /dT _A And sigma Q _ci Proportional to the ratio. The positive and/or negative numbers are summed and the sum over the change in AHU temperature yields a slope.

The flow rate indicates the slope of the power consumption. By measuring the flow rate, the slope of the power or energy as a function of temperature is given.

Since the slopes are in different directions, the heating sum and the cooling sum have opposite signs. The heating aggregate includes heating coils 16 of the AHU 12 and heating coils 26 of the terminal unit 22. The cooling aggregate includes cooling coils 17 of the AHU 12 and cooling coils 27 of the terminal unit 22.

The heating and cooling slopes are added for the total energy usage versus the slope of the supply air temperature change of the system. The flow rate has added to it an efficiency factor that is used to weight the energy consumption by the efficiency of the component. Because the AHU 12 and the terminal unit 22 have opposite roles, the opposite sign of the heating and cooling flow at the terminal unit 22 is opposite to the heating and cooling at the AHU 12.

In addition to or instead of collecting data indicating the amount of air being heated and cooled at the terminal, the controller 14 may collect an indication of where the energy consumption break point 40 occurred. The breakpoint 40 corresponds to the temperature set point of the terminal unit 22 and the temperature of the outside air is mixed by the AHU 12. The break point 40 in the total energy curve corresponds to the primary break point in the end controller 24: the point at which reheating starts or the point at which reheating stops. If the supply air temperature varies by some other selected amount, the breakpoint 40 may instead be indicated by the amount of air to be adjusted at the terminal unit 22. For example, the breakpoint 40 is found by determining whether the terminal unit 22 will still reheat if the supply air temperature is 2 degrees higher. A breakpoint 40 corresponding to the optimized supply air temperature is then identified. Once identified, the HVAC system may operate on each side of one or more break points 40 to identify a minimum slope magnitude.

Controller 14 is configured to set the AHU temperature based on the slope. A smaller slope corresponds to a more optimal operation of the system. The zero slope of the total energy is the optimal operation or energy consumption. If the total slope is zero or near zero (e.g., within 0.2), the system operates at a minimum or nearly minimum energy point. The supply air temperature is maintained or set to the current temperature with a slope of 0 or within a threshold tolerance of 0.

There may be multiple zero or low slope regions so false minima can be avoided by starting the test operation at random or spaced apart (e.g., cold, hot, and medium) start points of the air supply temperature.

The controller 14 is configured to adjust the supply air temperature upward if the slope is negative or negative and its magnitude is above the tolerance threshold. If the total slope is negative, the air supply temperature is too low and adjusted upward. For example, according to FIG. 2, if the AHU supply air temperature is 60 degrees, the slope is negative and therefore the AHU supply air temperature is increased. The controller 14 is configured to adjust the supply air temperature downward if the slope is positive or positive and its magnitude is above the tolerance threshold. If the total slope is positive, the air supply temperature is too high and adjusts downward. For example, according to FIG. 2, if the AHU supply air temperature is 73 degrees, the slope is positive and therefore the AHU supply air temperature is reduced.

The setting may continue to find an optimized slope. The power consumed at each coil is summed to see how it varies as the temperature of the air supplied by the air handler varies. To increase the supply air temperature, the cooling power at the air handler decreases, the heating power at the air handler increases, the cooling power at the terminal increases, and the heating power at the terminal decreases. By reading the air flow generated by the current setting, the slope can be determined again. The setting is performed again until the current setting is maintained.

The step size or adjustment in the setting may be a default amount, such as 1, 2, or 3 degrees. The amount may be programmed or selected by the user. In one embodiment, the adjustment is based on the magnitude of the slope. The magnitude or rate of supply air temperature adjustment is related to the magnitude of the total slope. For example, for a supply air temperature of 50-52 degrees, the adjustment amount will be larger than for a supply air temperature of 53-65 degrees. Any resolution may be used, such as providing two or more steps mapped to two or more slope magnitude ranges.

FIG. 3 illustrates one embodiment of a method for optimizing HVAC. Flow rates on heating and cooling components in an HVAC system are used to determine the slope of power consumption from air supply temperature or humidity. The slope is used to adjust the air supply temperature or humidity to optimize the energy consumption of the HVAC system.

The method is implemented by the system, controller 14, server, computer, panel, workstation, or another device of fig. 1. For example, the controller 14 receives an air flow rate from a communication interface or memory. Controller 14 calculates the slope and adjusts the settings for the air supplied by the AHU. The AHU 12 and/or the terminal 22 conditions the air based on the settings of the air supplied by the AHU.

The method is performed in the order shown or in other order. For example, act 58 is performed concurrently with other acts. Additional, different, or fewer acts may be provided. For example, an action is provided for establishing a set point or measuring the outside air temperature.

In act 52, the controller 52 receives an amount of air for heating or cooling for each terminal unit 22 that is supplied with air by the AHU 12. And also receives an air amount for heating or cooling by the AHU 12. Any measurement of the amount of air may be used to provide the desired amount of heating or cooling. For example, the air flow rate and whether to be used for heating or cooling is received from each of the terminal units 22 and the AHU 12. The sensors 19, 29 measure the operation of the air treatment in the HVAC system. The controller 14 may collect or store additional information, such as set points.

The measurement results and/or other data are transmitted to the controller 14. Any data is transmitted once or over time. The later transmissions may only transmit the changed data. The transmission is wired or wireless. The transmission is direct or through a network. In one embodiment, the transmission is by the controller 14 accessing or looking up data in memory. Any transport format may be used. The air quantity providing the measured air for heating and cooling is transmitted for use by the controller 14.

In act 54, controller 14 calculates a slope of energy usage by terminal unit 22 and AHU 12. The heat transfer function indicates the energy used to transfer heat or cold from the AHU 12 to the supply air and to the air output by the terminal unit 22 to the user space. This slope is used for temperature changes where the temperature change of the supply air from the AHU 12 is optimized. Using the heat transfer function, the slope is determined by the amount of air flow required to achieve heat transfer. The slope of energy usage is calculated from the air quantity (such as the sum of the flow rates from the different cooling and heating coils 16, 26, 17, 27). The controller 14 calculates the slope as the sum of the efficiency weighted heating and cooling slopes. The heating ramp is the sum of the amounts of air used to heat the air by the terminal unit 22 and the cooling ramp is the sum of the amounts of air used to cool the air by the terminal unit 22. The slope corresponding to the amount of air heated or cooled by the AHU 12 is also included in the heating or cooling aggregate. Alternatively, the total air flow from all heating and cooling devices is summed.

In one embodiment, the calculation of the slope of the energy usage of the overall system is divided into one or more sub-processes for calculating the airflow for each terminal unit in the system and another sub-process for calculating the airflow for the AHU controlling such terminal units. Another sub-process determines the total energy consumption. Other methods may be used, such as calculating different slopes for the end unit and the AHU, and then calculating the-total slope. The controller may also make a decision depending on the heating and cooling slopes of the end units or other factors used to derive an optimal slope for system energy usage.

The slope may be calculated using an efficiency factor (e.g., by heating, cooling, and/or coil). The power generated by the temperature change can be weighted by the efficiency of the temperature change. Different efficiencies may be allocated for heating versus cooling, for the AHU 12 versus the terminal unit 22, and/or through separate heating and cooling coils 16, 26, 17, 27.

In act 56, the controller 14 adjusts the air supply temperature or humidity of the AHU 12 based on the slope. The set point for the temperature or humidity of the air output from the AHU 12 to the terminal unit 22 is set to the same or a different value. When the slope is positive, the air supply temperature of the air handling unit decreases, and when the slope is negative, the air supply temperature increases. In the case where the slope is zero or substantially zero (e.g., 0.3 to-0.3), the set point remains at the same value.

This slope is used to see how the power consumed varies with the temperature or humidity of the air supplied by the air handler unit 12. For example, the temperature of the AHU supply air to the terminal unit 22 is controlled for optimization. To increase the supply air temperature, the cooling power at the air handler decreases, the heating power at the air handler increases, the cooling power at the terminal increases, and/or the heating power at the terminal decreases. The slope indicates whether to increase with decreasing AHU supply air temperature or to provide an opposite change.

In act 58, air provided to the user is conditioned. The air supplied by AHU 12 is conditioned. The terminal unit 22 heats or cools the air to a set point. Because the temperature of the air supplied by the AHU 12 is optimized, the total energy usage of the system 10 is optimized. Due to the optimization, each given terminal unit 22 may have a greater or lesser variation in air temperature across the heating coil or cooling coil.

The AHU 12 outputs air at a temperature or humidity established based on the slope of energy consumption, which is measured from the air flow in the system components. One or more of the terminal units 22 may further condition the air to a temperature or humidity specific to the corresponding user space. For example, some terminal units heat air to some different set point above the AHU supply air temperature and other terminals cool air to some different set point below the AHU supply air temperature. The conditioned air is output to the zone corresponding to the terminal unit 22.

Using the energy consumption slope of the air flow based measurement, energy consumption of the HVAC system is optimized with respect to the controlled variable. For example, the temperature of the air conditioned by the AHU 12 is set to provide a minimum or less level than other levels of energy consumption. Energy consumption is represented by heat transfer because energy is consumed at the AHU 12 and/or the terminal unit 22 to transfer heat or cold. Different set points and/or outside air temperatures may be generated as optimal or superior to other different temperatures or levels.

While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the invention. Furthermore, the various features, elements, and embodiments described herein may be claimed or combined in any combination or arrangement.

Claims

1. A control system for heating, ventilation and air conditioning, the control system comprising:

an air handling unit, AHU, comprising an AHU heating coil and an AHU cooling coil, the AHU configured to output supply air at an AHU temperature;

a terminal unit having a terminal flow rate sensor and having terminal heating and/or terminal cooling coils, the terminal unit being connected to the air handling unit by a conduit for receiving the supply air from the AHU;

a controller configured to receive a flow rate from the terminal flow rate sensor, calculate a slope of total power consumption of the air handling unit AHU and the terminal unit based on the flow rate, the slope being a function of the AHU temperature, and set the AHU temperature for the supply air based on the slope to minimize the total power consumption depending on an outside air temperature and a temperature set point for the terminal unit.

2. The control system of claim 1, wherein:

the AHU includes the controller; and

the AHU is connected to receive outside air from outside the building and is configured to heat or cool the outside air to generate the supply air according to the AHU temperature set based on the slope, and wherein the terminal unit has an air output connected to a user zone and is configured to heat or cool the supply air based on a temperature set point of the user zone.

3. The control system of claim 1 wherein the terminal unit is one of a plurality of terminal units that are group members with the AHU and the AHU is a group master, and wherein each terminal unit is configured to transmit a respective flow rate from a respective terminal unit that is one of the group members.

4. The control system of claim 1, wherein the controller is configured to one of:

calculating the slope in response to a change in outside air temperature or a change in a temperature set point of one or more of the terminal units; or (b)

The slope is calculated as the sum of the flow rates.

5. The control system of claim 1, wherein:

the controller is configured to calculate the slope from a heating sum of flow rates for heating and a cooling sum of flow rates for cooling; and

the controller is configured to calculate the slope as a sum of the heating sum and the cooling sum.

6. The control system of claim 1, wherein:

the controller is configured to calculate the slope from a heating sum of flow rates for heating and a cooling sum of flow rates for cooling;

the heating sum is a function of a heating efficiency factor and the cooling sum is a function of a cooling efficiency factor, the heating efficiency factor being different from the cooling efficiency factor; and

the slope is a function of an AHU efficiency factor that is different from the heating efficiency factor and the cooling efficiency factor.

7. The control system of claim 1, wherein the controller is configured to one of:

setting the AHU temperature to a current temperature if the slope is 0, adjusting the AHU temperature downward if the slope is negative, and adjusting the AHU temperature upward if the slope is positive; or (b)

The AHU temperature is set by an adjustment based on the magnitude of the slope.

8. The control system of claim 1 wherein the terminal unit is one of a plurality of terminal units connected to the AHU by a conduit to receive the supply air from the AHU, and wherein the controller is configured to calculate a slope of the power consumption as a function of a respective flow rate from a respective terminal flow rate sensor and a flow rate from the AHU.

9. A method for optimizing heating, ventilation and air conditioning, the method comprising:

receiving an air flow rate for heating or cooling air supplied to each terminal by the air processing unit;

calculating a slope of total power consumption of the terminal and the air handling unit from an air flow rate of air supplied by the air handling unit, the slope being a function of air handling unit temperature; and

the air supply temperature of the air handling unit is adjusted based on the slope to minimize the total power consumption depending on the outside air temperature and the temperature set point for the terminal.

10. The method of claim 9, wherein receiving the air flow rate for each terminal comprises: an air flow rate is received for each terminal and an indication of whether each terminal is heating or cooling air from the air handling unit is received.

11. The method of claim 9, wherein calculating the slope comprises: the slope is calculated as the sum of a heating slope for heating the terminal end of the air and a cooling slope for cooling the terminal end of the air.

12. The method according to claim 9, wherein:

calculating the slope includes calculating from an efficiency factor; and

the efficiency factor is one of a heating, cooling, or coil efficiency factor.

13. The method of claim 9, wherein adjusting comprises: the air supply temperature of the air handling unit is reduced when the slope is positive and the air supply temperature is increased when the slope is negative.

14. A control system for heating, ventilation and air conditioning, the control system comprising:

an air handling unit, AHU, having an AHU flow rate sensor, an AHU heating coil, and an AHU cooling coil, the AHU configured to supply air to a terminal at an AHU temperature; and

a controller configured to receive flow rates from the AHU flow rate sensor and a terminal flow rate sensor, calculate a slope of total power consumption of the air handling unit AHU and the terminal based on the flow rates, the slope being a function of an AHU temperature, and set the AHU temperature for supply air based on the slope to minimize the total power consumption depending on an outside air temperature and a temperature set point for the terminal.

15. The control system of claim 14, wherein the controller is configured to calculate the slope as a sum of a heating sum of flow rates for heating and a cooling sum of flow rates for cooling.

16. The control system of claim 14 wherein the controller is configured to set the AHU temperature to adjust the AHU temperature downward if the slope is negative and to adjust the AHU temperature upward if the slope is positive.